Telomeres are repeating DNA sequences (TTAGGG) together with proteins at the ends of linear chromosomes. They work as protective "caps": they stop the cell from mistaking the natural end of a chromosome for a DNA break and triggering emergency repair.
With each cell division telomeres shorten by roughly 50–100 base pairs — a kind of division "counter". When they become critically short, the cell stops dividing (the Hayflick limit). Telomeres can be rebuilt by the enzyme telomerase, and the stability of the ends is maintained by the protein complex shelterin.
Structure and length
A telomere consists of thousands of repeats of the sequence TTAGGG and ends in a short single-stranded "tail". This tail folds into a loop (the t-loop), which hides the very end of the chromosome. At birth human telomeres are about 10,000–15,000 base pairs long and gradually decline with age.
Why telomeres shorten
The cause is the "end-replication problem": DNA polymerase cannot fully copy the very edge of a linear molecule, and with each duplication the cell loses a piece of the telomere. Oxidative stress "eats" additional length. So in most cells of the body, where telomerase barely works, telomeres shorten throughout life.
Telomeres and aging
When telomeres reach a critical length, the cell enters an irreversible halt of division — cellular senescence. Short telomeres are linked to age, mortality and age-related diseases. That said, lifespan correlates better not so much with absolute length as with the rate of shortening. Telomere length is sometimes used as one of the biomarkers of aging, but it is a "noisy" measure, and it alone cannot precisely name biological age.
Can this be influenced
There is as yet no reliable way to safely lengthen telomeres in humans. Healthy sleep, physical activity, not smoking and controlling inflammation are linked to slower shortening. Artificially activating telomerase theoretically "rejuvenates" the cell, but carries a risk: this is exactly the mechanism cancer cells use to divide endlessly.
Calculate using this marker
Calculators where Telomeres is used directly:
Frequently asked questions
Can telomeres be lengthened?
There is no reliable and safe way to lengthen telomeres in humans. Lifestyle (sleep, movement, not smoking, controlling inflammation) mainly affects the rate of their shortening, not lengthening.
Will a telomere-length test show my biological age?
Only very roughly. Telomere length is a "noisy" biomarker: it varies greatly between people and tissues, so it alone cannot precisely determine biological age.